CVE-2026-20074Cisco IOS XR Software Multi-Instance Intermediate System-to-Intermediate System Denial of Service Vulnerability
- 7.4HighCVSS base score
- 0.18%Exploitation in 30 daysEPSS · top 92% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
A vulnerability in the Intermediate System-to-Intermediate System (IS-IS) multi-instance routing feature of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause the IS-IS process to restart unexpectedly. This vulnerability is due to insufficient input validation of ingress IS-IS packets. An attacker could exploit this vulnerability by sending crafted IS-IS packets to an affected device after forming an adjacency. A successful exploit could allow the attacker to cause the IS-IS process to restart unexpectedly, resulting in a temporary loss of connectivity to advertised networks and a denial of service (DoS) condition. Note: The IS-IS protocol is a routing protocol. To exploit this vulnerability, an attacker must be Layer 2-adjacent to the affected device and must have formed an adjacency.
Timeline
ID reserved
By cisco
- 5 months later
· 5 months later
Published
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| ciscoCNA (assigner) | 3.1 | High7.4 | CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H |
| NVDNVD · Analyzed | 3.1 | High7.4 | CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H |
- EPSS (exploitation in 30 days)
- 0.18% · top 92% of all CVEs (13 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.4.
Affected products
- affected 7.8.1
- affected 7.9.1
- affected 7.10.1
- affected 7.8.2
- affected 7.8.22
- affected 7.9.2
- affected 7.11.1
- affected 7.9.21
- affected 7.10.2
- affected 24.1.1
- affected 7.11.2
- affected 24.2.1
- affected 24.1.2
- affected 24.2.11
- affected 24.3.1
- affected 24.4.1
- affected 24.2.2
- affected 7.8.23
- affected 7.11.21
- affected 24.2.20
- affected 24.3.2
- affected 24.4.10
- affected 25.1.1
- affected 24.4.2
- affected 24.3.20
- affected 24.4.15
- affected 25.2.1
- affected 25.1.2
- affected 24.3.30
- affected 24.4.30
- affected 24.2.21
- affected 25.2.15
What to do
Exploitation: The Cisco PSIRT is not aware of any public announcements or malicious use of the vulnerability that is described in this advisory.
References
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-11219 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-20074)Record last updated .